Utility power is typically made available as an AC power signal distributed from one or more centralized sources to end users over a power distribution network. However, utility power is unavailable for certain structures. For example, movable structures such vehicles do not have access to utility power when moving and can be connected to power distribution network when parked only with difficulty. Similarly, remote structures such as cabins and military installations not near the utility power distribution network often cannot be practically powered using utility power.
DC power systems including batteries are often employed to provide power when utility power is unavailable. For example, trucks and boats typically employ a DC power system including a battery array to provide power at least to secondary vehicle electronics systems such as communications systems, navigation systems, ignition systems, heating and cooling systems, and the like. Shipping containers and remote cabins that operate using alternative primary power sources such as solar panels or generators also may include DC power systems including a battery or array of batteries to operate electronics systems when primary power is unavailable. Accordingly, most modern vehicles and remote structures use battery power sufficient to operate, at least for a limited period of time, electronics systems such as secondary vehicle electronics systems.
The capacity of a battery system used by a vehicle or remote structure is typically limited by factors such as size, weight, and cost. For example, a vehicle with an internal combustion engine may include a relatively small battery for use when the engine is not operating; a large battery array is impractical for vehicles with an internal combustion engine because the size of the batteries takes up valuable space and the weight of the batteries reduces vehicle efficiency when the vehicle is being moved by the engine. All electric vehicles have significantly greater battery capacity, but that battery capacity is often considered essential for the primary purpose of moving the vehicle, so the amount of battery capacity that can be dedicated to secondary vehicle electronics systems is limited. Battery systems employed by remote structures must be capable of providing power when the alternative power source is unavailable, but factors such as cost, size, and weight reduce the overall power storage capacity of such systems.
Heating and cooling systems have substantial energy requirements. Vehicles such as trucks or boats typically rely on the availability of the internal combustion engine when heating or cooling is required. When heating or cooling is required when the vehicle is parked or the boat is moored for more than a couple of minutes, the internal combustion engine will be operated in an idle mode solely to provide power to the heating and cooling system. Engine idling is inefficient and creates unnecessary pollution, and anti-idling laws are being enacted to prevent the use of idling engines, especially in congested environments like cities, truck stops, and harbors. For remote structures such as cabins or shipping containers, heating and cooling systems can be a major draw on battery power. Typically, an alternative or inferior heating or cooling source such as a wood burning stove, fans, or the like are used instead of a DC powered heating and cooling system.
The need thus exists for heating and cooling systems that operate using DC power having improved efficiency to optimize the use of battery power.